This article is from the CD-Recordable FAQ, by Andy McFadden (firstname.lastname@example.org) with numerous contributions by others.
HFS is the Hierarchical File System, used by the Macintosh. This is often
used instead of the ISO-9660 filesystem on Mac CD-ROMs, making the disc
unusable on systems that don't support HFS. As of Mac OS 8.1, an updated
filesystem called HFS Plus is available.
At present, the systems that can natively read HFS CD-ROMS are Macs, Amigas
(with AmiCDROM), PCs running Linux or OS/2 (with appropriate patches),
the Apple IIgs, and SGI machines running Irix (they appear as AppleDouble
Windows machines can read HFS disks with the appropriate
software. One example is "Conversions Plus" from Data Viz,
http://www.dataviz.com/products/conversionsplus/. Others include
MacDisk, from http://www.macdisk.com/prospen.php3, and HFVExplorer from
Some authoring packages for the Mac and Windows allow the creation of
"hybrid" CDs that have both an ISO-9660 filesystem and an HFS filesystem.
Such discs can be used on non-Mac systems, but still have all the file
attributes (creator type, resource fork) that Mac OS likes.
Apple has defined some ISO-9660 extensions that allow Macintosh files to
exist with file and creator types on ISO-9660 CD-ROMs. A description of
the extension is available as tech note FL 36 from: